Re: Tek 465 Negative 8 volt rail issues


Dave Peterson
 

Thanks Toby and Barry,

I'm becoming partial to Nichicon, not because I think their documentation is better, but I am becoming more familiar with it. And their capacitor series. I've found their Series charts very useful: https://www.nichicon.co.jp/english/products/alm_larg/index.html But I enjoyed reading and learning more about the large power supply cap types. So thanks for the app notes.

I am a bit concerned that the lifetime specs are so much less than the U** series caps, but I see that the "Large Can" types are intended for higher voltage. It's difficult to find a 1200uF, 100V U-series cap, but the "Large Can" L-series can handle that easily. But at a cost of lifetime/ripple current?

LGN2C122MELA40: 1200 uF, 160V, 25/40mm, 3000 hour lifetime @105C, 2300mA ripple current.
UHW1K122MHD: 1200uF, 80V, 16/40mm, 10000 hour lifetime @105C, 3500mA ripple current.

The application is a 465 C1513 which is filtering the unregulated 55v supply. Schematics, and measurement, shows this output is really in the range of 70+ volts. So very near the limits of U-series cap. The existing cap is a 100v cap, so we'll say that's the spec? But the U-series cap above has significantly better lifetime and ripple current. Which is the more important selection criteria here?

And then for the lower voltage, but higher value +15v, +5v, and -8v: the U-series again has significantly higher lifetime and ripple currents at the expense of a lower voltage rating, but still greater than the application. For example: UHE1E562MHD (5600uF, 25v, 10000h, 4200mA) vs. LGY1H562MELA40 (5600uF, 50v, 5000h, 2300mA)

The 1200uF cap seems a little on edge at 80v for U-series. But, within voltage spec, doesn't lifetime and ripple trump the ratio: spec voltage/operating voltage?

Dave

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